Flutter – Why am I getting a Null error without a null value?

I am trying to access a foreign-key field in a Supabase database using Flutter. None of the table rows has a null value when I view them on the Supabase dashboard, however, when I run my app in the simulator, I am getting an exception on line 53 (title: Text(data[‘payee(name)’]),) and I cannot figure out why. Examining the variable in the sidebar shows

• data = Map (4 items)
• 0 = "id" -> 2
• 1 = "date" -> "2019-05-01"
• 2 = "amount" -> 1290
• 3 = "payee_id" -> Map (1 item)
• key = "payee_id"
• value = Map (1 item)
• 0 = "name" -> "Goosehead Insurance"
• index = 0

The code for my view follows:

class HomePage extends StatelessWidget {
  HomePage({super.key});
  final SupabaseClient supabase = Supabase.instance.client;

  Future<List> readData() async {
    final result = await supabase.from('transactions').select('''
    id,
    date,
    amount,
    payee_id (name)
    ''');
    return result;
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('Supabase Course'),
        actions: [
          IconButton(
            onPressed: () async {
              await supabase.auth.signOut();
            },
            icon: const Icon(Icons.logout),
          )
        ],
      ),
      body: FutureBuilder(
        future: readData(),
        builder: (BuildContext context, AsyncSnapshot snapshot) {
          if (snapshot.hasError) {
            return Center(
              child: Text(snapshot.error.toString()),
            );
          }

          if (snapshot.hasData) {
            if (snapshot.data.length == 0) {
              return const Center(
                child: Text("No data available.n Create new data"),
              );
            }
            return ListView.builder(
              itemCount: snapshot.data.length,
              itemBuilder: (BuildContext context, int index) {
                var data = snapshot.data[index];
                return ListTile(
                  title: Text(data['payee(name)']), // <---error here!
                  trailing: IconButton(
                    onPressed: () {
                      Navigator.push(
                          context,
                          MaterialPageRoute(
                              builder: (context) =>
                                  EditPage(data['id'].toString(), data['id'])));
                    },
                    icon: const Icon(Icons.chevron_right_outlined),
                  ),
                );
              },
            );
          }

          return const Center(
            child: CircularProgressIndicator(),
          );
        },
      ),
    );
  }
}

The error I get on line 53 is "_TypeError (type ‘Null’ is not a subtype of type ‘String’)" but, as I said, there’s no null values in the table, and the variable inspector doesn’t show any null values. I cannot figure out what the problem is.